Using magnetic force upset welding to form T-joints between dissimilar thickness parts. This type of resistance welding is used to join compressor and turbine parts thereby reducing the weight and cost of a jet engine

Holko, K. H.

Moore, T. J.

English

NASA Technical Reports Server

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546
REPLY TO
ATTN OF: . GP NOV 2 8 1973
TOt RSI/Scientific & Technical Information Division
Attention: Miss Winnie M. Morgan
FROM: GP/Office of Assistant General Counsel for
Patent Matters
SUBJECT* Announcement of NASA^-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. patent No.
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA patent Case No.
, C
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
Yes / / No /W
Pursuant to Section 305(a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of the actual
inventor (author) appears at the heading of column No. 1 of
the Specification, following the words "... with respect to
an invention of ..."
Elizabeth A. Carter
Enclosure
Copy of patent cited above
NASA-HQ
https://ntrs.nasa.gov/search.jsp?R=19740003187 2020-03-17T14:20:19+00:00Z
United States Patent
Holko et al.
tin 3,770,933
[45] Nov. 6, 1973
154)
[75|
[73J
[22]
[62|
[52]
[51]
[58]
APPARATUS FOR WELDING BLADES TO
ROTORS
Inventors: Kenneth H. Holko, Strongsville;
Thomas J. Moore, Berla,
both of Ohio
Assignee: The United States of America as
represented by the Administrator
of the National Aeronautics and
Space Administration
Filed: Apr. 24, 1972
Appl. No.: 247,055
Related U.S. Application Data
Division of Ser. No. 134,658, April 16, 1971.
U.S. Cl 219/107, 219/101, 219/78,
29/497.5
Int. Cl B23k 11/04
Field of Search 219/101, 102-104,
219/107, 78, 86, 62, 99; 29/497.5,498, 471.7,
497
[56] References Cited
UNITED STATES PATENTS
2,776,362 1/1957 Welch 219/86
3,053,971 9/1962 Busse 219/107
2,905,804 9/1959 Wakeley 219/86
2,948,804 8/1960 Schueler 219/86
Primary Examiner—R. F. Staubly
Assistant Examiner—L. A. Schutzman
Attorney—N. T. Musial et al.
[57] ABSTRACT
Using magnetic force upset welding to form T-joints
between dissimilar thickness parts. This type of resis-
tance welding is used to join compressor and turbine_
parts thereby reducing the weight and cost of a j'*j*
gine.
5 Claims, 5 Drawing Figures
PATENTED HOV 61973 3.770,933
16 18
FIG. I
50
38
iUfflK42 48
46 /
3,770,933
1 2
APPARATUS FOR WELDING BLADES TO ROTORS A further object of the invention is to provide a resis-
RPI A-rcn APDI N-A-rinw tance Weldin8 apparatus for joining blades to rotors of
KtLA 1 tD APPLICA FION lightweight jet engines.
This application is a division of copending applica- These and other objects of the invention will be ap-
tion Ser. No. 134,658 filed Apr. 16, 1971. 5 parent from the specification which follows and from
the drawing wherein like numerals are used throughout
ORIGIN OF THE INVENTION
 to identify1ike parts.
The invention described herein was made by the em- DESCRIPTION OF THE DRAWING
ployees of the United States Government and may be
manufactured and used by or for the Government for 10 In the drawing
governmental purposes without the payment of any F1G- 1 is a vertical section showing an unbeveled
royalties thereon or therefor. blade positioned in electrode tooling constructed in ac-
cordance with the invention for welding to a rotor;
BACKGROUND OF THE INVENTION FIG. 2 is a partial view, in elevation, of the inside sur-
This invention is concerned with producing high 15 face of the tooling and is shown at a right angle to FIG.
quality welded joints between sections of greatly differ- J • ustrating an alternate embodiment of the invention
ent thickness. The invention is particularly directed to uUJ£n« an mse? In t.he.end ?*' el'C?O?f *O°1™?'
... . . ..
 r
 ,. .
 J
 , FIG. 3 is an enlarged view of the end of a blade which
welding compressor and turbine blades to rotors and . , . . . . ...
..
 r
 has been beveled prior to welding;
_, '. , . , ., .. 20 FIG. 4 is a simplified diagram of the magnetic forceCast blades are customarily used in compressors and
 we,di . an(J
turbines. These blades have large bases wh.ch are re-
 FIG g ., a lot of ka, curfent and force waves
ceived by mating slots in a drum. Thick drums are re-
 used jn magnetic force upset welding
quired so that the slots can be cut sufficiently large to
receive the blade bases. These factors increase the
 25 DESCRIPTION. OF THE PREFERRED
weight of a jet engine. EMBODIMENT
It has been proposed that compressor and turbine Referring now to the drawing, there is shown in FIG.
blades be joined to rotors and disks by welding. How- j
 a portj0n of a lightweight jet engine fabricated in ac-
ever, most of the conventional welding processes are cordance with the present invention. A plurality of
not readily applicable to making a T-joint between sec- 30 blades 10 are resistance welded to a rotor 12.
tions of greatly differing thicknesses because the thin- One of the blades is shown mounted in an electrode
ner sections are heated more rapidly than the thicker 14 prior to welding. This electrode forms tooling that
ones. This produces poor quality welds because the must be capable of holding each blade 10, conducting
heating is not concentrated at the interface formed at high currents during operation, and transmitting upset
the T-joint junction. 35 forces to the blade bases.
Resistance welding has been suggested for these ap- The electrode 14 is comprised of two sections 16 and
plications because maximum heat is developed at the 18 that are assembled by bolts and pins. Both sections
interface where resistance is high. However, in the con- 16 and 18 are of an electrically conductive material,
ventional move of several cycles or more of current, such as copper, that is capable of conducting high cur-
there is sufficient time for unequal heat dissipation to rents. All bolts, pins, and locating buttons used in as-
occur away from the interface. Weak welds result from sembling the sections 16 and 18 are made of nonmag-
this insufficient interfacial heating. net'c material to prevent the establishment of magnetic
Electron beam welding has also been suggested for fields which m'8ht deflect and disturb current flow- A11
attaching blades to drums. However, this procedure is
 4S conducting surfaces of the electrode 14 are silver
both costly and complicated. Plated to decrease the contact resistance and minimize
pitting of the electrode from welding spatter.
SUMMARY OF THE INVENTION A spacer 20 is positioned between the section 16 and
These problems have been solved by the resistance l* of the ?lec£°?e !*' Jhe spa"r co"tacts the upper
welding apparatus of the present invention which uti- 50 ?dge °f *%.£!* IT* I'"8 °PeratIon-
,. i • • • i i . j u » i-r Spacers 20 of different thicknesses can be used to varylow imtial electrode pressures, short welding ^ ^^
 Qf ^  ^ 1Q d ^  ^^ ^
times, and high welding current densit.es. These fea-
 The f 2Q also transfefs atic and magnetic
tures are combined with the application of a delayed,
 forces from ^ electrode 14 to the blade The
rapidly rising magnetic force to concentrate the heating
 20 js ,ikewise of a nonmagnetic electrically conducting
effect at the interface between the dissimilar thick- 55
 materia, such as CQpper
nesses rather than in the bulk material.
 The ,ower surface of the electrode surface 16 which
OJBECTS OF THE INVENTION faces the rotor 12 has a chamfered end portion 22 adja-
' cent the blade 10. The electrode section 18 has a simi-
It is, therefore, an object of the present invention to ,ar chamfered end portion 24. The chamfered surfaces
provide apparatus for joining members of dissimilar ou
 22 and 24 determine the contour of the welded blade
thicknesses by resistance welding with little or no melt-
 blase An anguiar contour at the joint between the
ing of the parent material. More particularly, the solid- blade 10 and the rotor 12 reduces the stress concentra-
state and/or fuson modes of resistance welding are tion. A chamfer of 45 degrees has been satisfactory to
used.
 6j form a fillet as the junction of the blade 10 and rotor
Another object of the invention is to provide welded 12.
components for a low-cost, lightweight small jet air- It is also contemplated that a radius can be formed on
craft engine. the surfaces 22 and 24 instead of the straight 45 degree
3,770,933
3 4
chamfer shown in FIG. 1. Such a radiused chamfer will solid line 56 represents the force used during welding,
produce a similarly radiused fillet at the weld. As the faying surfaces of the blade and rotor are
Referring now to FIG. 2 there is shown wedge shaped brought into contact, a pneumatic force shown by the
inserts 25 and 26 in the electrode 14. These inserts are upward curved portion 58 is applied. This force is
used to shape the current and heating patterns at the 5 maintained during the welding cycle,
interface between the blade and the rotor. The inserts A preheating current from the weld transformer 52
25 and 26 are preferably molybdenum and are properly illustrated by the dotted line 60 is passed through the
positioned by a copper block 27. The inserts and the platens 32 and 34. This preheat current is regulated by
block are chamfered along the lower edge. the weld voltage control 54. After a very short time
The lower edge of the blade 10 that is to be welded 10 delay of about 0.5 millisecond, caused by mechanical
to the rotor 12 extends outward from the lower edge of inertia in the welding head, a preheat magnetic force is
the electrode 14. This extension is extremely important applied by the magnetic force control 50. This mag-
in forming the weld at the proper location. This weld netic force is illustrated by the curved portion 62 in the
should be formed at the interface between the lower solid line. The small preheat half-cycle provides both
edge of the blade and the rotor surface. The extension 15 macro- and microalignment between the blades and ro-
is determined by the thickness of the spacer 20. tor, incipient solid-state welding, and an increase in in-
The lower edge of the blade 10 shown in FIG. 1 is terfacial temperature.
substantially flat. The sides adjacent to this lower edge A welding current illustrated by the dotted line 64 is
may be beveled at 28 and 30 as shown in FIG. 3. By then passed through the blade and rotor. The welding
beveling the blade 10 the initial contact thickness is 20 half-cycle 64 provides the bulk of heating necessary in
changed. Also by changing the bevel angle the shape of the formation of the weld. After a small welding time
the final weld between the blade 10 and the rotor 12 is delay of about 1.5 milliseconds a weld magnetic force
changed. . illustrated by the curve 66 in the solid line is applied by
FIG. 4 is a simplified diagrammatic view of the appa- the magnetic force control 50. This magnetic force 66
ratus for welding the blades 10 to the rotor 12 in accor- 25 js approximately five times the pneumatic force 58.
dance with the invention. This apparatus includes an This magnetic force 66 is used to upset the heated
upper platen 32 and a lower platen 34 shown in FIGS. blade and form a fillet at the chamfers 22 and 24 as the
1 and 4. The upper platen 32 is movably mounted and tooling 14 moves from the position shown in FIG. 1 to-
carries the electrode tooling 14. The lower, platen 34 is ward the rotor 12.
mounted on a fixed base 36. The upper platen 32 is se- 30 The magnetic force upset welding utilized in the pres-
cured to the lower end of a reciprocable shaft 38 hav- ent invention differs from conventional resistance
ing its upper end connected to the piston of an aircylin- welding in that the forge force is applied by a 120 hertz
der 40. • electromagnet. The advantage is that the force-waves
A magnet armature 42 of a 120 hertz electromagnet can be timed in duration and phase shifted in relation
is connected to the shaft 38 between the air cylinder 40 35 to the current half-waves as illustrated in FIG. 5. The
and the upper platen 32. A magnet stator 44 mounted heating is more effectively developed and concentrated
below the armature 42 encircles the shaft 38. The ar- at the interface in this manner. By delaying the initia-
mature 42 is adjustably mounted on the shaft 38 to en- tion of the force half-wave after the initiation of the
able the magnet air gap between the armature 42 and current half-wave, the current flows through an inter-
the stator 44 to be suitably adjusted. A copper coil 46 40 face between the blade 10 and the rotor 12 that is
is wrapped about the stator 44 and is electrically con- under low pressure and has high electrical resistance,
nected to a secondary winding of a magnet transformer In this manner the resistance is high during current flow
48. The primary winding of the transformer 48 is con- which increases the resistance heating at the interface,
nected to magnetic force control equipment 50. This precise timing within very short weld current times
A weld transformer 52 in a magnetic force upset is essential for welding unequal sections. The magnetic
welder has its primary winding connected to weld volt- force upset welding utilizes high welding current densi-
age control equipment 54. The secondary winding of ties and short current times. By way of example, the
the transformer 52 is connected.to the upper platen 32 welding current density is generally greater than 1 X
and lower platen 34. The weld voltage control equip- 106 amperes per square inch, and the welding time is on
ment 54 varies the current which passes through the the order of one one-hundred-twentieth second. The
electrode tooling 14. electromagnetic forging blow is precisely times with re-
in operation, the blade 10 is mounted in the elec- spect to the welding current.
trode tooling 14 with the upper platen 32 in a raised po- A microscale liquid phase may be produced at the
sition. The space between the blade 10 and the rotor 12 faying surfaces during magnetic force upset welding-,
forms a break in the welding transformer secondary of Any molten material present tends to be forced out of
the magnetic force upset welder. ' ' the joint when the forging blow is applied. The resul-
The blade 10 is brought into light contact with the tant weld can be either entirely solid-state or a combi-
rotor as shown in FIG. 1 by moving the piston in the air nation of solid-state and fusion. The absence of molten
cylinder 40. The faying surfaces of the blade 10 and ,- material at the joint assures minimum chemical segre-
rotor 12 arc maintained in contact by pneumatic pres- gation and minimum residual welding stress. Heat input
sure transmitted through the spacer 20. The blade 10 to the joint is very low and is largely confined to the re-
is then resistance welded by solid-state and/or fusion gion immediately adjacent to the faying surfaces. This
modes to the rotor 12. low heat input is quite desirable from a metallurgical
Referring now to FIG. 5 there is shown a plot of cur-
 6J standpoint.
rent and force waves used in magnetic force upset Wave initiation, duration, and magnitude are depen-
welding. These waves are less than one cycle of 60 'dent upon the setting of the weld control equipment 54.
hertz current and two cycles of 120 hertz force. The In the case of the magnetic force wave, the magnet gap
3,770,933
may be adjusted as previously described to vary the
force magnitude at one control setting. By adjusting
this control setting and the magnet gap the time rela-
tion between the force initiation and the current initia-
tion is varied while the force magnitude is held rela- 5
tively constant.
While the preferred embodiment of the invention has
been described it will be appreciated that various struc-
tural modifications may be made without departing
from the spirit of the invention or the scope of the sub- 10
joined claims. By way of example it is contemplated
that the invention may be used for positioning the
blades 10 on the rotor 12 prior to electron beam weld-
ing. Indexing the blades could be precisely done by nu-
merical control. After the blades have been resistance 15
welded to the rotor as previously described an electron
beam weld is made at the fillets.
What is claimed is:
1. Apparatus for resistance welding blades to rotors
comprising 20
mating sections of an electrically conducting non-
magnetic material for holding one of said blades,
conducting an electric current thereto, and trans-
mitting upset forces, each of said mating sections'
having chamfered portions for contouring the 25
welds, spacer means between said mating sections
for controlling the distance said blade extends'from
said sections and for transferring pneumatic and
magnetic forces to said blade,
pneumatic means for moving said mating sections 30
and said blade into contact with said rotor and
maintaining the faying surfaces of said blade and
said rotor in contact by applying a substantially
constant pneumatic force to said blade and said ro-
tor,
a source of electric current connected to said mating
sections for passing high welding current densities
through said contacting blade and rotor for short
periods of time to heat the same at said faying sur-
faces,
magnetic means for applying rapidly rising forces to
said contacting blades and rotor through said mat-
ing sections during said heating to upset said blade
and form a weld at the faying surfaces, and
means for delaying the application of said magnetic
forces for a short period of time after the passage
of said heating currents.
2. Apparatus as claimed in claim 1 including a
straight chamfer along an edge of each mating section
facing the other member to be welded to form a fillet
in the weld.
3. Apparatus as claimed in claim 1 including a radi-
used chamfer along an edge of each mating section fac-
ing the other members to be welded to form a fillet in
the weld.
4. Apparatus as claimed in claim 1 including inserts
in said mating sections to shape the current and heating
patterns at the interface between the contacting mem-
bers.
5. Apparatus as claimed in claim 4 wherein the mat-
ing sections are copper and the inserts are molybde-
num.
35
40
45
50
55
60
65


Apparatus for welding blades to rotors

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